It is generally believed that "vocal hyperfunction" is an underlying component in a majority of voice disorders, but there is a paucity of hard data concerning: l) specific physiologic and acoustic manifestations of vocal hyperfunction, and 2) the actual role of hyperfunction in the development and maintenance of various voice disorders. Thus, the primary goals of this project are to develop and use measures to: l) provide objective descriptions of conditions referred to as "vocal hyperfunction", and 2) add to existing knowledge concerning "normal" voice production in a way which will aid in interpreting data on hyperfunctional voice production. These goals will be accomplished through the use of a unique combination of non-invasively obtained indirect measures which should delineate relationships between underlying physiological mechanisms and acoustic characteristics of voice production. These measures will include: parameters derived from inverse-filtered approximations of the glottal air flow waveform, estimates of glottal resistance and vocal efficiency, measures of vocal intensity and fundamental frequency, and electroglottographic estimates of vocal-fold contact patterns. These measures will be related to information gathered from medical examination of the larynx and auditorily-based judgements of voice quality. Data will be obtained from five groups of subjects (2 non-pathologic and 3 pathologic) designed so that the nature of hyperfunction can be studied in dysphonias that exist: l) in the absence of organic pathology, and 2) in benign vocal pathology believed to be the result of abuse/misues of the voice. The experimental design is motivated by a set of interrelated hypotheses which form a descriptive "model" of vocal hyperfunction. Data analysis and interpretation will be related to this model. The results are expected to provide new information about hyperfunctionally-related voice disorders which is based on objective measures. Such information should help in the differential diagnosis and in understanding the role of hyperfunction in the development and maintenance of various voice disorders. Measures which turn out to be the mose relevant for describing vocal hyperfunction should also have future clinical utility as diagnostic tools and as means for studying therapeutic efficacy.